There have been many technical papers written about dense phase and dilute phase conveying, and whether the system should be a negative or positive type of system; however, there often seems to be lack of definitive information that plant engineers can use to clearly define their own system. It’s similar to getting lost when a local gives directions because instead of giving a straightforward route, the unfamiliar are led through a maze of back roads.
Just as there are various factors given consideration when planning a route to a destination, such as time, distance, conditions, purpose and safety, there are many factors to take into account when designing a pneumatic conveying system to deliver a finished product to a packaging line.
In packaging operations, the most common pneumatic conveyor systems are vacuum conveying systems, but before heading into that topic, a basic understanding of the components that make up a pneumatic conveyor system is essential.
A standard pneumatic conveying system consists of five basic pieces of equipment that come together to work as one:
The selection of a pick-up point depends on the type of container used to store materials or products. If the product is in drums or box, then a pick-up wand, inserted into the container, may be used to pull material from the container into the convey tube. When material is stored in bags, ergonomic bag dump stations that reduce spillage are often utilized. This allows the emptied material to fl ow by gravity into the vacuum conveying line. For supersacks or large totes, bulk bag dischargers are frequently the choice as a pick-up point.
From the pick-up point, material fl ows through convey tubes to the vacuum receiver. There are a number of different types and sizes of vacuum tubes that are utilized and chosen, depending upon application. Vacuum receivers transfer material from above the packaging machinery through discharge valves on the bottom. The material is conveyed from the pick-up point to the vacuum receiver until it reaches a pre-determined load, or is “made”, then the discharge valve opens and the material drops into the packaging machine.
Vacuum producers are the core of pneumatic conveying systems and work with the control panel to manage the fl ow of material through the convey tubes to the vacuum receivers. Two of the most common vacuum producers are venturi powered units that run on compressed air, and positive displacement pumps that run on electricity; and, each has its advantages and disadvantages.
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